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BEAM Solar Chariots 

Make] Projects 

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build, hack, tweak, share, discover, ■ 

BEAM Solar Chariots 

Written By: Zach and Kim DeBord 



Drill and bits (1) 
Heat gun or hair dryer (1) 
Needle Nose Pliers (1) 
Safety glasses (1) 
• Small screwdriver (1) 

Soldering Iron and rosin core solder (1) 

Transistor. 2N3904 ("3904") NPN (2) 
from RadioShack. 

Transistor. 2N3906 ("3906") PNP (2) 
from RadioShack. 

Flashing LED (2) 
from RadioShack. 

1/4W 2.2k ohm resistor (2) 
from RadioShack. 

4.5 volt solar cell (2) 

Hook up wire (1) 
from RadioShack. 

4700|iF Capacitors (6) 
from RadioShack. 

Cassette tape mechanisms (2) 
from a microcassette player or other 
source for low-power DC motor. These 
are fun to hunt down in thrift stores or 
via online auction. You can also salvage 
the pulley, drive belt, and rubber back 
wheel from the player. 

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BEAM Solar Chariots 

1 • 

Heat Shrink tubing (1) 
from RadioShack. 

Brush-on Future Glue (1) 
from RadioShack. 

#2-56 hex nuts (1) 
from RadioShack. 

#2-56 machine screws (1) 
from RadioShack. 

1/8" - Telescoping metal tubes (1) 
can be found at your local hobby store. 

Socket Pins (optional) (4) 

1/8" Birchwood or other strong, 
lightweight material (1) 

Paint (1) 


BEAM robot building techniques allow you to build fun and simple little robots with lots of 
room for stylizing. BEAM robots can move anywhere from a fraction of an inch to a couple of 
feet, depending on how big their capacitors are. You can also use batteries. For these two 
projects, we'll use what's known as a "solar engine" (Type 1 "FLED" variety), some store- 
bought and scavenged electronics, and laser-cut and gold-leafed wheels to build some stylin' 
little Solar Chariots. Let the build begin! 

BEAM is a type of robot design that allows you to create little robot/robot- 1 ike critters and 
vehicles mainly using basic analog components (resistors, transistors, capacitors, diodes, 
LEDs). The challenge is to try and get as much robot-like behavior using these components. 
BEAM is an acronym for "Biology, Electronics, Aesthetics, Mechanics" and these four 
elements serve as inspiration in all BEAM design. You can find our more about BEAM on our 
BEAM robot page . You can find out more information on the FLED-type solar engine of the 

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BEAM Solar Chariots 

Step 1 — Preparing the LED 

• Cover the LED with some heat shrink tubing, tape, or opaque paint. 

• We're not actually using the LED as a light, we're using it as a conductor that will 
trigger the discharge phase of circuit. 

• To shrink the tubing, if you don't have a heat-gun, you can use the tip of a soldering 
iron or a lighter. Hold the heat-source closer and closer to the tubing until it starts 
to shrink. 

• Be careful with your heat source and close in slowly until the material starts to 
shrink. Don't melt it or set it (or you!) on fire. 

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BEAM Solar Chariots 

Step 2 — Preparing the Transistors 

• Paint the top of the 3906 transistor so you can identify the part later. 

• Glue the two transistors together with the flat parts of them facing each other. 

• Apply some heat shrink tubing around the transistors so you don't have to wait for the glue 
to dry. 

• Flip the transistors over. Make sure to keep the 3906 on top. 

• Bend and trim the legs according to the images. The two touching leads should be 
soldered together. 

• Consult the illustration in Step 3 if you have trouble seeing how the transistor leads 
(legs) are connected. 

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BEAM Solar Chariots 

Step 3 — Assembling a Solar Engine 




• Solder on the LED. Make sure the negative lead (shorter leg) connects to the negative wire 
of the solar panel. Make sure the positive lead connects to the center lead on the 3906. 

• Solder on the 2.2KQ resistor as indicated in the illustration. Unlike the LED, it is not 
polarity sensitive and it doesn't matter what direction the resistor faces. 

• Solder on the three 4700uF capacitors, in parallel, hooking them up to the positive and 
negative leads as show in the diagram (only one is depicted in the image for simplicity's 

• Solder on the motor, as shown in the diagram. 

• Congratulate yourself. You now have a FLED-based BEAM solar engine built. 

• This solar engine is called a FLED-type, which stands for "Flashing LED." When the 
circuit has charged up enough to flash the LED, it acts as a conductor which allows 
electricity to flow through it and trigger the discharge phase of the circuit, sending precious 
power to our chariots. 

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BEAM Solar Chariots 

Step 4 — Circuit Tweaking and Troubleshooting 

• If your LED is blinking, try raising your resistor value. Try within the 1KQ to 10KQ range 
(we started with a 2.2KQ resistor). 

• Different color LEDs require different amounts of voltage. From lowest to highest: 
Red, Green, Blue, White. 

• If you hear a high pitched pulsing a lot of times, the easiest fix is finding a more efficient 
motor. That sound means the motor isn't getting enough power to turn over. 

• Only very efficient motors work well in this circuit. Try hooking up your motor to the 
circuit/cell and feel the amount of torque it's delivering to the motor shaft. If it feels strong 
(an educated guess), then you can try hooking it up to the chariot. 

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BEAM Solar Chariots 

Step 5 — Printing the Templates 


Mm -•■■V.'U -.1:1- 

• If you haven't already done so, 
download the Chariot Racers 
template here . 

• The Symet template has a 0.428" 
hole in the center for a motor and 
three 0.637" holes for capacitors. 
Cut to fit your parts. The rest of the 
holes we added for decoration. 

• If you have capacitors that 
are larger than the holes in 
the template, you'll have to enlarge 

• The rest of the structural 
components will be used to make 
our solar roller. 

• The overall diameter of the wheels 
are 3.5". 


Step 6 — Making a Symet Chariot 

• The first Chariot we'll build is called 
a Symet in BEAM parlance ("sym" 
for symmetrical). Symets are little 
BEAM tops that store the sun's 
charge in capacitors and then 
dissipate it for a spin. 

• The Symet balances on a DC 
motor's axle which spins to make 
our top move. 

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BEAM Solar Chariots 

Step 7 — Apply Creativity Here 

• We used a laser cutter and 1/8" 
birch plywood to cut out our 

• You can also choose to apply gold 
leaf to the top for full Chariot effect. 

• Cardboard, wood, and plastic are 
great materials you can use, too. 

• In the right hands, scissors, and a 
hobby knife blade are just as good 
as a laser cutter. Be creative if 
lasers aren't in your neighborhood 

Step 8 — Assemble and Attach Solar Engine 

• Slide some heat shrink tubing over the top of the motor and capacitors (as seen in the first 
image) and slide them into position. 

• A couple drops of super glue can help hold parts in position. 

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BEAM Solar Chariots 

Step 9 — Test Run Your Top 

• Parts can get heavy in a hurry. Make sure you've got the right mix of enough voltage from 
your flashing LED and power required to turn your salvaged motor over. 

• If your LED is flashing you might need a larger resistor. 

• If nothing happens, check all of your connections. These little guys can be fragile. 

Step 10 — Making a Solar Roller Chariot 

• Now let's use the same type of 
solar engine to build a type of 
BEAM vehicle known as a solar 

• For this solar roller chariot, we've 
salvaged extra parts from an old 
microcassette player to drive our 
bot. We'll use the same 
configuration of three 4700uF 
capacitors as our power source. 

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BEAM Solar Chariots 

Step 11 — Scavenged Components 

• For our solar roller, we harvested a 
wheel, motor, pulley, belt, and 
screws from the guts of a 
microcassette player. 

• You can use the same laser-cut 
and gold leaf treatment on the roller 

• Don't forget: One aspect of 
the BEAM ethos is 
"Aesthetics." This offers an 
opportunity to really get creative 
and make something that looks 
really cool and expresses your 

• BEAM robots also 
frequently make use of 
scavenged parts. Many BEAMbots 
are made entirely of techno-junk. In 
the past, we've used old hard 
drives' disks, cardboard, or cut-up 
plastic jugs for roller wheels. 

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BEAM Solar Chariots 

Step 12 — Attach the Motor 


• Connect a motor to the rear of the 
main body component for the 
chariot. There are two different 
body templates. One allows for a 

1 .2" motor to be pushed through 
(shown here). The other allows for 
a pancake motor to be attached. 

• Put a 0.3" long piece of 1/8" metal 
tubing in one of the eight holes 
(seen to the left in the image) on 
the body component, appropriate to 
the length of your drive belt. Use 
super glue and heat shrink tubing 
to keep the tube in place. The axle 
for our two large chariot wheels will 
go through here. 

• Use screws taken from the 
cassette player to secure the motor 
to the body. 

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BEAM Solar Chariots 

Step 13 — Attach Rear Wheel 

• A roller wheel harvested from the 
cassette plater serves as a back 

• A small C-clip holds the rod 
of the wheel assembly in 
place. You can use pliers to 
carefully push the rod out, thus 
pushing off the C-clip in the 

• The rod is then press-fitted though 
a hole of your choosing on the 

Step 14 — Make Your Wheels 

• Laser-cut out the wheels (found in the template in Step 4). Use a lower power setting when 
cutting the design so as not to cut though the wheels. Flip the wheels over and engrave 
spots for where to glue the wheel extenders. Note: You will have to freeze and unfreeze 
layers in the drawing files to keep parts aligned. 

• Glue the wheel extenders onto the wheels. Two extenders go on each side of the wheels. 

• Glue the brass pulley from your cassette player onto the wheel extender with the larger 

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BEAM Solar Chariots 

Step 15 — Attach Wheels and Axle 

• Glue a 0.62" length of the smaller hollow tubing over the axle of the pulley. This will be the 
axle that the other wheel will be attached to after the wheels are on the body component. 

• Make sure the wheel with the belt pulley lines up with the motor. 

• Some oil in the spacer tube helps the wheels turn more freely. 

• Put one wheel in and connect the other side with some glue. The wheels should easily 
rotate in the spacer tube. 

• Attach the belt from the motor to the pulley. 

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BEAM Solar Chariots 

Step 16 — Final Assembly 

• Attach the FLED circuit to the body 
with a zip tie, then solder the motor 
wires to it. 

• Attach the solar cell simply by 
soldering it onto your solar engine 
circuit, making sure positive and 
negative are correct as per the 
illustration in Step 3. 

• As you can see from the 
images, we just used the 
leads from the transistors to 
provide the structural connection to 
the chariot. Besides making it 
easy, it also allows you to adjust 
the angle of your cell for maximum 
light exposure. 

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BEAM Solar Chariots 

Step 17 — You're Off to the Races! 

• Now you're ready to put your 
BEAM Chariots into some bright 
sunlight (or artificial light) and 
watch them charge up and activate. 
Make more than one of each type 
and have a race. 

• For the Solar Roller, once 
you've made and tested 
one, you can try making more and 
tweaking the design to cut down on 
weight, reduce friction, use a larger 
capacitor to store more power (if 
you used a capacitor) and other 
improvements. You can learn a lot 
by this trial-and-error process. 

• Most of all, have fun! 

This document was last generated on 201 2-1 1 -02 05:53:21 PM. 

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